GlossaryAdvanced
Replay Attack
Reusing a previously valid transaction, potentially on a different network, without authorization.
A replay attack involves rebroadcasting a previously valid, signed transaction — potentially on a different network that shares transaction formatting with the original, such as after a contentious hard fork — without new authorization from the original signer.
Networks that fork from a shared history sometimes need specific replay-protection measures to prevent a transaction on one chain from also being valid, unintentionally, on the other.
Examples
- A hard fork without proper replay protection can let a transaction on one chain be unintentionally replayed on the other.
- Replay protection is a common, deliberate safeguard added specifically around contentious network forks.